Field of the Disclosure
The present invention relates generally to power factor correction circuits in a power supply, and more specifically, the invention relates to increasing efficiency of a power factor correction circuit.
Background
Power supplies are typically used to convert alternating current (“ac”) power provided by an electrical outlet into usable direct current (“dc”) power for an electrical device. One important consideration for power supply design is how efficiently power is delivered to the power supply. To improve power delivery efficiency a power factor correction (PFC) circuit may be used in the power supply. More specifically, a power factor correction circuit attempts to shape the current waveform as closely to the shape of the voltage waveform.
Typically, PFC circuits are designed to include a power switch that is controlled to switch between an off state and on state in order to transform a distorted input current waveform transmitted from the distribution line into a more ideal current waveform that resembles the shape of the input voltage waveform. More specifically, the power switch is coupled to an energy transfer element to transfer energy to the output of the power supply. However, during operation the PFC circuit experiences switching losses that are created in the power switch due to parasitic capacitances. Typically, parasitic capacitance can be defined as an unwanted capacitance that exists between parts of an electrical component due to their proximity to each other. Additional losses are also realized in the energy transfer element.